This article throws light on the sixteen components of polluted water and their impact. They are: 1. Oil and Derivatives, 2. Carbonic Compounds, 3. Thermal Pollution, 4. pH, 5. Heavy Metals, 6. Biodiversity in Water, 7. Suspended Impurities, 8. Algae and Bacteria, 9. Silts and Sediments, 10. Oxygen Demanding Wastes and Others.
Component # 1. Oil and Derivatives:
Two different kinds of oils are encountered as water pollutants. The first type includes animal and vegetable fat, consisting of triglyceride esters formed between glycerol and fatty acids of varying chain lengths.
The second type of oil is the liquid fraction of crude petroleum or mineral oil.
Crude petroleum is a mixture of hydrocarbons. When petroleum is fractionated by distillation processes, it yields the more commonly recognised products gasoline, kerosene, metor oil, benzene, paraffin and purified mineral oil.
None of these fractions is edible or otherwise utilizable as nutrients by higher plants or animals. They are, in many circumstances, highly toxic because of their solvent properties. They also tend to coat cells and tissues, thereby interfering with the normal permeability of cells for nutrient uptake and by-product excretion.
Petroleum extracted from the area of continental shelf is transported from one country to another by ships through sea routes. If there is an accident or leakage during transportation, oil is spread hundreds of kilometers on the water surface and causes serious pollution problems.
According to an estimate one ton of oil is spilled for every million tons of oil transported, in other words, about 0.0001 per cent of transported oil is lost as spillage. The effluents discharged from the refineries contain plenty of oil and cause pollution of rivers around oil refineries. Oil is washed into rivers from spills on roads and factory floors, from workshops and garages.
The oil spill covers the water surface and prevents atmospheric oxygen from mixing with water and consumes much of oxygen itself for its own degradation. The oil film on the surface of water inhibits the photosynthetic activity of aquatic autotrophs and growth of plankton.
The reduced availability of oxygen in water, poisoning of food and toxic effect of oil cause death of aquatic animals. Sometimes oil spilled over water surface may catch fire and cause damage to aquatic life.
Component # 2. Carbonic Compounds:
It includes detergents and other cleaning materials, surfactants, pesticides and other organic industrial wastes. Many of these materials are poisonous for living organisms and cause serious water pollution problems. Detergents and other cleaning materials form an important source of water pollution. They change the pH of water and thereby the distribution and activities of aquatic life.
Synthetic detergents are not easily decomposed by bacteria and are rich source of phosphate that hasten the process of Eutrophication of water with frequent algal blooms which impart colour, odour and unpleasant taste to the water and may cause inconvenience in water supply and fish farming making the water further unfit for domestic purposes.
There is another group of organic pollutants known as phenols in domestic sewage and industrial waste water. These are the hydroxy derivatives of benzene.
Inorganic carbon also affects the eutrophication, which ultimately affects the chemistry of river. Toxic organic contaminants of agricultural origin in water stream are a common topic of discussion nowadays. Organic pesticides in a river of Buenos Aires and Argentina have shown alarming features.
Presence of particular organic compounds is responsible for specific odour. Some hydrophytes growing in carbon rich medium have capacity to absorb inorganic carbon for photosynthesis.
Seasonal variation in organic content is found in the water bodies. Organic phosphates have also been shown to be absorbed by some selected microorganisms. Dead and decaying plant parts fall in water and increase the organic content of the water body, in addition to the increasing load of the sediments; which is considered to be responsible for the death of most of the modern day lotic ecosystems.
Component # 3. Thermal Pollution:
Some industries discharge hot water directly in the water bodies which causes rise in temperature and results in thermal pollution. The important industries which cause thermal pollution are nuclear powers, power generators etc. where water is used as coolant, but nearly all the industries contribute for the above, though they vary in their extent.
Bacterial population reduction in response to thermal pollution has also been reported in some studies. Temperature also affects electrical conductance of water in addition to the oxygen content in water, which is also affected by temperature.
Rate of biodegradation of organic compounds increases by increase in temperature, this can be taken as positive as well as a negative contribution of the high temperature of the water body. Distribution of plants in an aquatic system with respect to temperature and light is now a common and well-known phenomenon. DO, BOD and COD, i.e. the oxygen budget, show large variation in relation to temperature.
Component # 4. pH:
pH is the negative log of H+ concentration present in a sample. A specific pH is essential for the normal survival of any organism. pH affects the enzymatic activity, thus indirectly affects the elemental mobilisation. pH also affects the distribution of plants. The study of changing phytoplanktonic composition as well as the macrophytic diversity with respect to lowering of pH has been reported through the studies in Canada.
Component # 5. Heavy Metals:
Heavy metals which were of no use in human life during a prominent period of evolution have now encroached into human life to a great extent. Due to Industrial Revolution or industrial based life, the importance of heavy metals has increased a lot.
At the same time, the right thing at wrong place has created great problems. Heavy metals are important components of colours and dyes and are also used in various pharmaceuticals and other industries.
The excess or surplus or unused heavy metals ultimately find its way into the water bodies. These components show biological magnification. They are active components, which forms chelates and interfere in biochemical reactions in human body. They are recognised carcinogenic and potent to reduce immunity and also to enhance impotentiality.
Heavy metals are present in a variety of industrial effluents. They are absorbed by hydrophytes as it has been reported in some of the aquaculture experiments using some selected plants. These metals also precipitate in the sediments along with the dead and decaying plant parts.
Chromium absorption by duckweed was reported. Chromium and Manganese uptake by Hydrilla and the same by mosses have also been reported in the recent studies.
Mercury in hydrophytes and herbivorous fishes has also been reported in studies; the path of the transmission of the heavy metal from the industrial effluents to the fishes, through the aquatic plants needs no further clarification.
Heavy metal content in various strata of rivers also varies. Due to nutrient absorption property of some plants they have been advocated to be the biological filter. This property of the selected plants can be utilised for eco-management of the polluted water-bodies.
Accumulation of Copper, Lead, Manganese and Iron by Hydrodictyon an alga is reported by some Indian scientists. Cadmium and Lead accumulation by rooted aquatic plants have been shown in some of the researches. Mercury, Cadmium, Lead and Thallium have been reported to be present in a nutrient rich lake. Bioaccumulation of Mercury and Chromium by certain blue green algae has been reported.
The microorganisms have great tendency to metabolize the heavy metals; this has been possible due to short life span of the microorganisms. Studies regarding the investigation of Lead and Zinc removal by Azolla and Lemna are also in progress. Zinc and Lead uptake by Lemna and any other aquatic plants including Eichhornia have been reported.
Metals were also reported in composted municipal waste through studies in China.
Lichen Peltigera has been reported to absorb Cadmium. Chromium accumulation in Ceratophyllum was reported in certain landmark researches in India. Cadmium accumulations in Eichhornia have been reported. Metals were also reported in composted municipal waste through studies in China. Lichen Peltigera has been reported to absorb Cadmium.
Chromium accumulation in Ceratophyllum was reported in certain landmark researches in India. Cadmium accumulation in Eichhornia has been reported in a number of studies. Silver has been reported to be present in the sediments of rivers and estuaries of Africa; the studies report.
Study of the behaviour of Lanthanide-920-dye complex in water is being studied. Response of metal dye complexes in waste is being explored in a number of studies.
Component # 6. Biodiversity in Water:
“Water is considered as the basis of life” comes true when rich biodiversity is found in water-bodies or the adjoining areas. Biodiversity along riparian corridors have been studied. The biodiversity of any aquatic ecosystem is also affected by pollution or the physicochemical condition of the water body and the adjoining area.
Fishes are very sensitive for water pollution and any change in the water quality compels the fishes to migrate. This becomes possible in lotic ecosystem, where the water is free flowing; but this becomes impossible in the case of a lentic ecosystem, where there is no way for the fishes, other than to sacrifice their lives or live diseased.
Occurrence of aquatic fungi in river Sutlej which varied seasonally was monitored by a group of scientists and it was also found that its population is affected by the pollution level. The population of bacteria and fungi in aquatic medium also depends upon the physicochemical factors of the water-body.
The slime fungi have been reported in sewage also. Various species of Eichhornia, which is an exotic aquatic weed has been found predominantly growing in polluted water-bodies. Eichhornia and other water hyacinths have been reported to absorb nutrients and thus act as pollutant scrubber.
Planktonic studies with respect to varying water quality parameters have been conducted. Limnological studies in fresh water are also attaining prime importance nowadays. Phyto-sociological study of aquatic plants in light of the Phyto-diversity is a basic study for sorting the plants as pollution indicator or the pollution scrubber.
If a plant is found growing luxuriantly in a polluted condition, this shows that it might be absorbing the pollutants.
On the other hand, if a plant is found growing feebly in a mildly polluted area, but totally absent from a heavily polluted zone, this indicates that the plant is pollution sensitive; such plants can be successfully used as the pollution indicators. This finding is subject to certain field trials.
Effect of hyacinths on fish population and also on the algal concentration has shown remarkable results. In the studies regarding the effect of thick hyacinth on water quality, the most remarkable results were found in the case of the oxygen budget, i.e. the DO was found greatly reduced, as compared to the control.
Pros and cons of aquatic weeds have been a matter of debate at most of the platforms in seminar and symposia based on the aquatics.
Methods to control aquatic weeds are an urgent need of the time to prevent the process of sedimentation. Submerged aquatic plants were advocated to be supporting to the aquatic life as they directly release the dissolved oxygen into the water-body. Different macrophytes also behave differently for different pollutants, especially for the metals and the heavy metals.
Metals have been detected in few water macrophytes, which were considered to be tolerant for the specific chemical and were found growing luxuriantly in the medium. Response of aquatic weeds on variation in nitrogen level is also interesting.
Nitrate and phosphate both promote the phenomenon of eutrophication, thereby blooming of algal community in addition to the macrophytic population. At the same time, the phosphate concentration is considered to be more important than the nitrate concentration for eutrophication.
Component # 7. Suspended Impurities:
Particles of an insoluble material may be held in suspension if their size and density are such that they do not settle or float to the surface. The particles can be either organic or inorganic in composition and the ability of a particle to remain in suspension is determined by physical and chemical factors such as chemical composition of the substance, surface charge on the particle, shape, size and density.
Component # 8. Algae and Bacteria:
In case of living particles, e.g. bacteria, algae and other microorganisms, the ability to counteract gravity motility is a significant factor, as is the change in buoyant density through production and accumulation of gas in vacuoles within cells. For example, many algae tend to settle from suspension in the dark but produce oxygen in the light (photosynthesis), which gives the cells buoyancy and ability to rise towards the surface.
Any particle suspended in water causes turbidity, which is an expression of the optical property of water. Suspended particles cause light to be absorbed or scattered, or both, rather than transmitted in straight lines.
Some of the more commonly encountered suspended materials are a variety of clay types and other soil types, detritus consisting of fragments of previously living organisms and their cells, living microorganisms, phytoplankton’s, zooplanktons, and finely dispersed chemical precipitates.
Component # 9. Silts and Sediments:
Soil which has been moved by wind, water or ice as the result of erosion and is then deposited in a receiving body of water is considered to be sediment.
Based upon size and chemical composition of the particles, sediments are divided into three categories:
(i) Sand—have a particle size range of 2 to 0.05 mm. It is high in quartz content and is relatively inert,
(ii) Silt—is usually defined as particles with a size distribution of 0.05 to 0.002 mm. Silt is also high in quartz as well as in feldspar,
(iii) Clays—consist of aluminium silicates less than 0.002 mm in size. Therefore most clay is of a type that can go into colloidal suspension.
Sedimentation i.e. the process of particles settling from suspension is directly proportional to the velocity of the particles in suspension and this is related to its shape, size and density. Suspended solids, i.e. turbidity, tend to reduce light penetration.
This can be either beneficial or detrimental—depending on circumstances and water use. For example, algal growth is generally retarded in highly turbid water caused by suspended silt and clay. If the water is used for drinking it may help in preventing disagreeable flavours and odours originating from by-products of algal metabolism.
In contrast, turbidity may be directly caused by high cell density of algae and bacteria, thereby producing disagreeable tastes and odours in the water. When the cells eventually die, they represent an organic load with a high oxygen demand.
Sedimentation is responsible for filling lakes and, over a period of geological time, results in conversion of a lake to a swamp. This process is referred to as lake aging and a dead lake is one that is filled with sediments.
Turbidity of water is affected by Suspended Particulate Matters present in the water. In view of its importance the “river Logger”, an instrument to monitor suspended Particulate Matters, has been designed. Trace elements were reported in the Suspended Particulate Matters of many rivers including some of the rivers in India.
Suspended Particulate Matters also affects the biotic community as studies indicate that visibility and the turbidity are affected by the Suspended Particulate Matters. Chemistry of water affects the chemistry of Suspended Particulate Matters and sediments, as the selected chemicals get desorbed over the Suspended Particulate Matters.
Component # 10. Oxygen Demanding Wastes:
Organic oxygen demanding wastes can be divided into two convenient categories, including those that are of a natural origin produced by biosynthesis, and those that are synthesised chemically. Virtually, all naturally synthesised organic molecules and many synthetic compounds can be attacked or otherwise degraded by the oxidative mechanism of aerobic organisms. The respiratory demand for oxygen by aerobic organisms.
The respiratory demand for oxygen by aerobic organisms while they use organic wastes as nutrients is known as biochemical oxygen demand (BOD). The oxygen demand can be enhanced due to domestic sewage, farm animal waste, manufacturing process waste, or any other direct addition of organic matter to water.
The practice of aerobic waste treatment is merely an attempt to supply sufficient dissolved oxygen to satisfy the oxygen demand of an increased organic load.
Any naturally produced organic compound is capable of being degraded by one organism or another, and, in an aquatic ecosystem, the potential exists for the presence of any specific microorganisms in a mixed population.
Many inorganic substances are products of organic degradation or are pollutants added directly to water. Many of these inorganic compounds represent an oxygen demand because they are either metabolised oxidatively by organisms or oxidised chemically under normal atmospheric conditions.
In balanced aquatic ecosystem, oxygen demanding substances are always produced but in amounts that allow the available oxygen supply to satisfy the demand. The ecosystem goes out of balance when an external source of oxygen demand is added as the result of human endeavour.
Relationship between DO, BOD and COD in river Ganga and similar comparative study in different other rivers have been conducted. Oxygen budget is directly or indirectly affected by the presence of toxic metals and heavy metals.
DO affect the potential of sewage treatment plants. DO of water is also affected by turbidity which restricts the solar radiations. Roots of aquatics contain chloroplast in their root. Any aquatic system is capable enough to balance the oxygen budget naturally in unmanned condition.
Component # 11. Pesticides:
Pesticides are generally categorized in relation to the pest to be controlled, such as insecticides, herbicides, fungicides, rodenticides. The more widely used pesticides are persistent, and their toxicity is of the broad spectrum type. Most of these pesticides are extremely toxic both to fish and to other aquatic organisms.
Pesticide in river water was been detected in a number of researches; as they are being used in sufficiently high quantities in agriculture. In some rivers the pesticides are reported to be the major and important water pollutants. Diquate-di-bromide, and important pesticide, has also been reported in aquatic ecosystem.
The acute toxicity value for aquatic organisms s expressed as a ‘Lethal concentration’ or LC 50 value, which is a statistical estimate of the pesticide concentration in water necessary to kill 50 percent of the test organisms within a specified time under standardised conditions.
Factors such as temperature, pH, salinity, turbidity and organic content of water may greatly alter the toxicity of a pesticide. Aquatic plants and animals can accumulate concentrations of certain pesticides many times greater than that in water. The greatest magnification is found with organochlorine insecticides.
Contamination of aquatic environments by pesticides poses a serious threat to equate life forms. Domestic water supplies are frequently the same systems in which aquatic life need to be protected from pesticide contamination. Thus the use of pesticides involves a risk great enough to have surface water criteria for public water supplies (Table 2.1).
Pesticides result soil pollution in various ways. Soil pollution assumes major concern in contaminating the crop growth, affecting soil pH, and microbial population, thus affecting the soil fertility.
Use of the less persistent pesticides, development of more target specific pesticides and the potential of biological control (insect parasites, predators and pathogens) might greatly reduce the risk to both man and other organisms.
Component # 12. Disease Causing Agents:
Wastes from municipalities sanatoria’s, tanneries, slaughtering houses, sugar mills, dairies, agricultural farms etc. discharged into different water-bodies are the potential sources of different infective and pathogenic agents like bacteria, viruses, protozoans, fungi, Platyhelminthes which cause several fatal and infectious diseases such as typhoid, cholera, hepatitis, scabies, trachoma, sleeping sickness, dysentery, yellow fever, amoebiosis, diarrhea, ascariosis distomatosis etc. in human beings.
Some important diseases of human being and their pathogens transmitted by polluted water are given in Table 2.2.
Microorganisms have been reported to be present in sediments of rivers as well as in ocean. Some microorganisms are helpful in removal of nutrients from the water-bodies, but their specific potential is still under investigation.
Underground water has also been reported to contain bacteria. Relationship between coliform bacteria and organic pollution level had been studied to facilitate in projecting the water treatment plants. Coliform number and Coli index has also been an important parameter under study.
Component # 13. Nutrients:
The elements nitrogen and phosphorus are essential to all life forms. They are also abundant in waste waters as phosphates, nitrates, and ammonia, or combined organic nitrogen. Nitrates and Phosphates which are most often present in the runoff water act as nutrients in the water-bodies and are considered the most important factors for eutrophication.
The source of these compounds in waste waters include discharges from domestic sewage treatment plants, wastes from the manufacture and use of fertilisers and wastes from other industries.
These compounds, when discharged to streams and lakes, contribute to excessive algal growth and subsequent eutrophication. Excessive algal growth can indirectly contribute to lowering of dissolved oxygen content of the water, due to high oxygen demand represented by the algae remains at the end of the season, or when sunlight is prevented from reaching the algal community by high turbidity in water.
Nitrogen in the un-oxidised ammonia state exerts an oxygen demand in waters. Nitrates show a tendency to migrate rapidly through groundwater. Surface waters containing excess amounts of nitrates are harmful to all animal life. High nitrate concentrations in receiving waters stimulate the growth of plankton and aquatic weeds. High nitrogen content in plant parts retards the rate of biological decomposition.
Excessive plant growth, however, can result in eutrophication of waters because the death and decay of the plants rob the waters of their dissolved oxygen. In human infants, methemoglobinemia (‘Blue babies’ disease) results from an increase of met-hemoglobin in the bloodstream caused by nitrites. Met-hemoglobin is the blood constituent that is incapable of transporting oxygen.
Phosphorus, in aquatic medium, also plays an important role in controlling its biodiversity. Phosphorus, an active element, does not occur free in nature. It is an essential nutrient for plant and animal growth and like nitrogen it passes through cycles of decomposition and photosynthesis.
Phosphorus is found in surface and ground waters, principally as phosphates. In water, phosphate ions exist as H2PO4– or HPO42- depending on the pH.
Phosphates are not found in significant concentrations in natural surface waters because they are readily metabolised by plants. Phosphates in receiving waters because, they are readily metabolised by plants.
Phosphates in receiving water originate especially from municipal sewage as a result of the large usage of synthetic detergents. Phosphates have been considered to be one of the most important key elements to excessive growth of aquatic plants with its deleterious effect on fish life and effect on eutrophication.
Denitrifying bacteria also play an important role in nitrogen concentration of a medium. Biological nitrification and de-nitrification was studied and is also being studied at length. Detailed investigation of nitrogen level in lotic ecosystem is gaining prime importance nowadays.
High nitrogen content in plant parts retards the rate of biological decomposition. Phosphorus in aquatic system is recycled by absorption by plants. Phosphorus in aquatic medium also plays an important role in aquatic plants. Nitrogen and phosphorus accumulation in water hyacinths has been common reporting.
Component # 14. Studies on Effect of Water Pollution:
One of the best rather worst properties of water is that it is a universal solvent. It dissolves nearly all the things coming in contact of it, excepting some organic compounds. It also has the tendency to keep the dissolved components along with it in the form of solution.
Another harmful property is its high permeability. During its course of movement from one place to another it carries the dissolved chemicals along with it.
Micro and macrophytes of the aquatic bodies lodge a lot of harmful chemicals in their body, that which is present in the water-body. From there hazardous components move into the zoological system via the process of feeding. In this way, ultimately, they reach the human body in a considerable concentration, through the process of eating and being eaten at the all the trophic level the chemical showing its presence.
This is not the only way, but we are so much used to water that no ritual can be completed without water. Further all the civilizations originated at the bank of rivers. Using polluted water in all the walks of life ultimately leads to ill-growth or in the form of a variety of unstudied and unidentified diseases, to human as well as to the cattle and to the plants.
Chemistry of water controls the distribution of the fishes in water bodies. Multidimensional approach for the study of water pollution rather, environmental pollution and its management is being promoted globally, as the academic boundaries between the subjects exist no more. Importance of the water quality of bathing water on health is also gaining attention in the higher society.
Component # 15. Seasonal Variation:
Distribution of macrophytes, zooplanktons and fishes not only depend on quality of water but also on the climatic condition. Actually, it is the climatic factor which regulates most of the parameters of the water. During summer, due to high temperature, the rate of evaporation is higher; as a result the water in the aquatic systems reduces. The pollutants more or less remain the same.
Therefore the water-bodies lentic or lotic become highly polluted. On the other hand, during rainy season, dilution of the water bodies takes place by addition of the rain water. The pollutants remain the same, therefore, during rainy seasons; they appear to be comparatively less polluted.
Component # 16. Indicators of Pollution:
Plants are more sensitive to pollutants than human or other biotic components. Therefore plants can best be used for the bio-indicator of environmental pollution. Sensitive species can serve as indicators and resistant species as accumulators which collect large amount of pollutants without damage.
Many chemicals, fertilisers, pesticides and fossil fuels release toxic substance into the environment that is taken up by the plants from their surroundings.
Nematodes have been identified as indicator of water pollution in Swartkops River in South Africa. A variety of aquatic macrophytes are recommended to be used as indicator of heavy metal pollution or for indicator of some other component of pollution.
Algal community as indicator of organic pollution in river Vishwamitri in Baroda has been recommended. Problems in the field of locating indicator plants for toxicity testing are tough but rewarding.